Paste



Patented Oct. 29, 1940 UNITED STATES PASTE H I Leonard G. Vande Bogart, Chicago, 111., assignor nois to Crane Co., Chicago, 111., a corporation of Illi- L,

No Drawing. Application September 11, 1937, Serial No. 163,397

1 Claim.

More particularly, my invention is concerned with an adhesive material serving as a protective coating.

It is one of the principal objects of this invention to provide a mixture which can be conveniently used in the temporary protection of glossy or polished surfaces during such times when these surfaces are likely to be subjected to mechanical abuse or to the attack of corrosive l0 chemicals, such as cleaning acids, paints, etc. Examples of the surfaces referred to are the surfaces of enameled iron, porcelain, vitreous china, and electro-plated plumbing fixtures; polished woodwork and the like, all of which may be subjected to abuse of the type mentioned during periods when new buildings are in process of construction or subsequently when the buildings may be undergoing renovation.

A suggested method of obtaining suchprotection is by covering the surface in-question with one or more layers of newspaper, causing these to adhere to the glossy surface and to each other by means of a suitable adhesive. Advantages-of this method are (1) the fact that old newspapers are usually available at no extra cost to the user, and (2) the added fact that soft unglazed paper of this type possesses the advantage that, when wet, it adapts itself readily to the irregular contours of surfaces such as those mentioned above.

However, among the objections of this method are the following:

Many of the adhesives which are now readily available are not suitable because they, themselves, mar the surface sought to be protected.

Contact between the surface to be protected and the wet newspapers, either with or without an intervening layer of adhesive, is often followed by staining of the former by constituents originally present in the newspaper.

It is therefore emphasized that a suitable adhesive is one which not only has the capacity of being able to hold the layer or layers of paper in place without being itself harmful to the surface to be protected, but it must also be capable of inhibiting or preventing the staining or corrosion of such surfaces by the constituents referred to and which are present in the paper used with the adhesive.

In order to combat the physical abuse to which such surfaces are subjected, it is particularly desirable that the protective layer comprising essentially the paper and the adhesive be capable of providing a considerable cushioning effect 5 in distinction to offering merely a thin dense layer between the critical surface and any physical force which may produce mars in that surface.

Other desirable features present in the adhesive exemplifying my invention are ease of 5 application and ease of removal, and chemical stability together with the absence of objectionable odor either during or after application.

Chemical stability, in particular, may be obtained through the use of suitable preservatives 10 in conjunction with the use of easily decomposable materials (e; g., starch, gelatin, casein, etc.). In the absence ofchemical stability'the effects of changes in composition may also-be overcome by the addition of special agents which 15 neutralize the reaction products and thereby prevent them from reacting with constituents in the surface to be protected.

In this invention I make use of an adhesive material which is both chemically stable and 20 which requires neither the use of a preservative to prevent decomposition nor the use of a neutralizing agent to overcome the effects of decomposition. The adhesive material referred to is a homogeneous chemical compound which is 25 knownchemically as a boro-phosphate resin, of the type known as sodium boro-phosphate. Since these sodium boro-phosphates are produced'by blending phosphoric acid and sodium tetraborate and processing them in a suitable so manner, the resulting products (typified by the commercial products known as Abopon) are completely inorganic in nature and cannot ferment and produce organic acids as do the common adhesives which are either animal or vege- 36 table origin. Mixtures making use of them, therefore, can be adjusted to an initial desired pH and. do not require the presence of antifermenting agents or chemical neutralizers to combine with fermentation products. Because 40 it contains in large proportion the borate and phosphate radicals it is, in addition to bein an effective adhesive, an efficient buffer agent against changes in the pH value of mixtures containing it which might result from the acci- 45 dental addition of small amounts of acids or alkalis. It lends itself to the preparation of mixtures which are to be marketed either as a dry powder, or as aliquid, or as a jell-like product. For the particular application which is 50 the subject matter of this invention I prefer the jell-like form, but it should be understood that either of the other two forms can be used.

In conjunction with this adhesive material I, use some other chemical which is capable of neutralizing any acid which may be present in the particular brand of paper which is to be applied by means of the paste or which may be spilled on the surface which has been covered by means of the paper and paste. In the case of liquid or jell-like mixtures I have used a water solution of borax. Other water soluble-alkaline materials could be used also since the adhesive is not incompatible with any of the common alkaline salts. For mixtures which are to be marketed as a dry powder, solid neutralizing agents may be used, as for example, zinc oxide, calcium carbonate, powdered borax, etc. It should be understood that these reagents are added for the purpose of neutralizing any acidity resulting from the leaching action of water on paper, or from the spilling of some acid solution on the surface in question. They are not added for the purpose alluded to in referring to other previous mixtures (to prevent the decomposition of the adhesive material or to overcome any acidity resulting from such decomposition), because in the mixture of this invention there is no occurrence of such decomposition.

In order to provide for the desired cushioning effect I prefer to add some solid material which, however, is soft and free from scratchy or abrasive-like particles. Typical of these materials are the colloidal clays known as bentonite; and asbestos fibre, the latter being particularly of the grade known as asbestine and which is commonly used in the manufacture of paints. The latter material is also naturally soft and voluminous while the former is capable of absorbing a large quantity of water and swelling to many times its original particle size. Because of this characteristic an excellent cushion for the purpose is obtained when alternate layers of paper and adhesive containing bentonite are built up on the surfaces to be protected and allowed to dry. Of the two solid materials mentioned I prefer bentonite because it material-1y improves the spreading power of the adhesive mixture and also because, after drying, it readily absorbs any water which may lodge on the protected surface and thereby tends to prevent contact between that surface and the water or the dissolved constituents in the water. Other clays do not possess this quality (the ability to absorb water) to anything like the same extent and, therefore, do not serve so well. While bentonite has been found to have some adhesive powers when dispersed in water I have found that this quality is lost as soon as the mixture dries; as a matter of fact, the aforementioned tendency to absorb water actually helps to weaken the adhesion and thereby facilitates the easy removal when suchremoval becomes necessary. This is particularly true when the paper usedwith the adhesive does not have'a glazed or otherwise water repellent surface. In this respect also bentoniteappears to be superior to other clays.

As a further feature of my invention I may also incorporate in the mixture some'material which tends to make the dried surface somewhat water repellent. Typical of such materials is aluminum stearate.

As an additional feature of my invention I may incorporate as a plasticizing agent either glycerine or some other liquid compound of high boiling point. If desired, I am able to use triethanolamine both as a plasticizi-ng agent and as a neutralizing agent in place of the aforementioned alkaline salts, such as borax and the like.

A typical mixture which has been found quite satisfactory for the purpose described contains 50 parts of bentonite, parts of water, 10 parts of glycerol, 15 parts of borax, and 5 parts of a heavy solution (sp. gr.=1.68) of boro-phosphate resin. It should be understood that these proportions may be variedconsiderably and still obtain a satisfactory mixture. For example, increasing the percentage of boro-phos-phate resin introduces no harmful effects but merely increases the cost while increasing the adhesiveness to a degree which however is-not required for this particular application. The percentage of glycerol may also be increased without introducing any harmful effects and also without any added benefits which justify the increased cost. The ratio between the amount of water and bentonite respectively required is determined largely by the ability of the latter to absorb water and which, in turn, also determines the consistency of the mixture. The proportions given above were selected because they are representative of and result-in a mixture which retains the same .consistency indefinitely; in other words, it does not separate into its constituent parts. The percentage of ,borax may also be varied. Less than that given has been found insuliicient in some cases and more may be required in other special cases. No trouble was experienced in mixing these materials. Bentonite, which is wet with difnculty by pure water, is readily we-t by the water solution of the other ingredients. It is not necessary to first intimately mix the bentonite and other powdered materials and then subsequently incorporate water into the mixture. Of course, when it is desired to market the paste in the form of a dry powder it will be necessary to follow the latter practice. It should, however, be understood that this is not the only way in which these materials can be mixed.

In considering the application of my mixture to the surface to be protected, it may be applied directly to such surface and then subsequently place the soft unglazed paper upon it, or else the adhesive mixture may be applied to the paper itself and then contact subsequently made with the surface to be protected.

It should become readily apparent to those skilled in the art that my invention is capable of numerous modifications varying from those disclosed and I desire, therefore, to be limited by the scope of the claim appended hereto.

I claim:

In a chemically stable cushioning adhesive for use in holding newspaper to glazed surfaces for protective purposes,-=the combination of ingredients comprising a mixture approximating 50 parts of bentonite, 150 parts of water, 10 parts of glycerol, 15' parts of borax and 5 parts of a heavy solution of boro-phosphate resin.

LEONARD G. VANDE BOGAR'I. 

